The proposed study is designed to (l) test the relative effectiveness of a teen-led versus adult-led 3-year school-based psychosocial drug abuse prevention program, SMART Moves, that begins in 7th grade; (2) test whether five sets of hypothesized mediating factors vary as a function of program participation and account for changes in youth alcohol, tobacco, and other drug (ATOD) use; (3) measure the extent to which program implementation factors contribute to the effectiveness of the teen-led and adult- led drug abuse prevention program; and (4) explore the contextual characteristics of program sites and the relationship between these school and community characteristics and implementation of the teen-led and adult-led SMART Moves drug abuse prevention program. The 5-year study will be conducted in 10 schools across Pennsylvania using the U.S. Department of Agriculture's Cooperative Extension Service delivery system of 4-H school enrichment programs (i.e., 4-H educational programs offered in the school setting). A Cooperative Extension Educator (CE Educator) in each of the 10 communities will manage the project in their collaborating school and will supervise implementation of the program by the teen and adult leaders. The study will employ an experimental design with a pretest and multiple posttests to test hypothesized mediators, implementation processes, and outcomes by comparing youth in three conditions (a teen-led program group, an adult-led program group, and a no-program control group). Quantitative and qualitative data will be collected on implementation processes across the three years of the program. Data on school and community contextual factors will be collected during each of the five years of the research. Findings from the proposed study will determine the utility of building CE Educator/school collaborations to admInister the SMART Moves program. If found effective, the program could be disseminated by CE Educators across the nation.